class Solution 
{
public:
    int mySqrt(int x) 
    {
        int left = 0, right = x;
        while(left < right)
        {
            long long mid = left + (right - left + 1) / 2;
            if(mid * mid <= x) left = mid;
            else right = mid - 1;
        }
        return left;
    }
};